Rotary earth boring tool with rolling cutters



Feb. 22, 1938. J. A. zuBLlN 2,108,956

ROTARY EARTH VBORING TOOL WITH vROLJ'JIIUI CUTTERS Original Filed M ach 50. 1936 2 Sheets-Sheet 1 Feb. 22, .vz-UBLIN Roummma '501mm Iwe oL wma mmv@ GUTTERS @riginal 'sind Maren an., 193s .2 Sheets-Sheet 2 Patented Feb. 22, y1938 Bonny EARTH noinNG Toor. wl'rn aoLL me `cu'r'rnas v John n. zubiingnps Annales,

application Miren o, 193e, vserial No@ Original 71,600.: Divided and this 1936, Serial.No.'90,799

application July .15,

zo om (ci ass-a1) cutters is that each cutter rollsin the same defl- This application is a truedivision of my application, Serial No. '71,600 filed March 30, 1936, now Patent No. 2,050,988, granted August 11, 1936, which contains the following disclosure:

5' The present'invention relates generally to ro tary` earth boring tools such as are used to drill oil wells, but more especially to drill bits having rotatingcutters and adapted to penetration of -relatively hard formations. A drill bit of a simi- Ser. No. 56,252, entitled Earth boring tool withrolling utters, filed December 26, 1935, now

PatentNo. 2,050,989, granted August 11, .1936., and the present invention is also in the nature` of an improvement thereon.

qui ments that make design dimcult. For best penetration, it is necessary to have only a minimum portion of the cutters in contact with the formation at any one time, as' higher pressure 25 per unit area increases. -th'epenetration of the teeth. On the other hand, to. keep the cost of drilling within reason by giving a long life to the bit, it is necessary to provide a maximum of cutting teeth on the'bit since` .the drilling life of a bit is generally proportional to the total number and size of` cutting teeth available to cut the formation;- and an increase in the total number of teeth has usually been accompanied.

by a like increase in the number of teeth cutting atA any one time.

drilling contact, at any one time, the remainder 40 serve, since it also does itsshare of the cutting after the first .active" portion movesfout 'of contact with the formation. In roller or cone..

bits of the lpresent type, all the roller or cone cutters are in simultaneous engagement with. the

`formation, so the reserve cutting surface -is limited to that portion4 of each cutter'not so engaged, and amounts to butl a few, perhaps three or four, times the active cutting surfaces; whereasbth the efficiency and the \l-if e of the bitI would be Aincreased by increasing the ratio between the reserve and active portions of the cutting surface.

' Another disadvantage of the conventional roller orcone'bit having but a small number of rolling lar kind is'shown in my companion application For -reasons that are well known in the art, successful drill bits-for use in rockand other, L hard formations almost always have rotatingv cutters since they produce the best kind of drillin motion. However, there are conflicting reting surface to be worn. y A

It is also -ariobject of the invention to provide It is thus'apparent that the ideall bitl has a. large total amount of cutting surface but hasV only a small part of that surface active, or inA of the lcutting surface being, in effect, in re nite path concentric to the bit axis as the bit is rotated'.- Since oftenonly one cutter, and rarely more than two cutters,A coveragiven area, thefailure of one or two cutters holdsup the entire bit when there is no. additional cutter -to per-,

the broken rollers. or cones.

I have found that when4 a member rotatable l' about an axis on a bit is brought into contact with the formation and the bit as 'a whole is rotated, therel is` a natural tendency for the i .i

member to rotate about its own axis relative to the bit. This'natural tendency i`s strong and positive, and can be used to move 'cutters into Thus it is a general-object of my invention both to decrease the amount ofactivecutting area which isat -any one time in .cutting posi tion, and to increase the amount .of rese've area. Thse changes have the effect of increasing the speed of penetration, and also of lengthening the bits life since there is more aggregatecuta bit which not only has the usual reserve cutting area on each cutter, but alsohas asumA ciently large number of cutters that several en tire cutters 'are in reserve, an'd, as a whole, are

each successively brought into cutting position and then returned to the reserve or non-cutting the ratio between reserve and active portions of the aggregate cutting surface is in form cuttingfoperations in the area covered-'byy .and out of contact with the formation if 'those Y. 'cutters are carried on the rotatable member.

position.- By having entire.cutters.,h ivreselfve, y 'I creased to several 'times that possible when all formation.

cutters are simultaneously in contact withthe A further object of the invention -is .to .providea' bit, having a plurality 'of cutters which are moved overl varying paths non-concentricrelative to the bore hole center, so that all cutters Veventually move across substantially all points ioll on the' hole Abottom'arid the complete failure of one cutter does not prevent removal of formation atany point.

Another obj-ecris to provide a bit having4 the above characteristics in-whichthe roller cutters. contact the formation with a' substantially t'rue rolling motion throughout all, or substantially all, of their'engagement with'the formation, thus disintegrating 4the formation with a crushing` action.

Another object 'is to` provide a bit in whichfthe cutters are moved successively from cuttingposition upward to a position where they are cleaned M yantages of my invention are attained will be` by the circulation fluid and then returned downwardly to the digging position.

It is another principal object of theinvention to provide a bit with a plurality of rotatable cutter carriers rotated' by their naturall tendency to turn when in contact with the formation, the speed and direction of rotation being determined by.this natural tendency. y It is another object to provide -a bit with `a plurality of rotatable cutter carriers rotating in accordance with their natural tendency to turn, .f the position on the carriers of ,thev cutter axes being such as to advance or retard the rotating speed of the carriers, and also to add a slicing motion .to the substantially true-rolling motion of the rollers.

And it is a further object toprovide a bit with a cutter assembly in which the rolling cuttersmay be of different widths, spacing, dimensions and shapes and with different numbers of teeth, thus forcing the cutters and their teeth into different paths in order to make tracking diiicult and improve cutting efciency.

'I'hese objects are attained ina bit constructed according t0 my invention by providing thebit shank, which is attached to -a drill stem to be rotated thereby about its vertical axis, with one or more, preferably two, wheel-like cutter carriers rotatably -mounted on the shank. Each cutter carrier is placed at one side, orsubstanytially so, of the vertical4 bit axis, and when two carriers are used they jare placed-on opposite sides of lthis axis. The carriers rotate about horizontal axes in the preferred'forms of my invention, but the axis may be inclined if desired. Around the periphery of each carrier is mounted a plurality of rolling cutters of any suitable type which "extend radially beyond the. carrier and, as the carrier rotates these cutters are moved into and out of cutting contact with the formation. Through these cutters, l the carrier contiacts the formation and is turnedas a result when the bit is rotated by the drill stem. f

In my copending application above mentioned, a similar rotatable cutter carrier is provided 'with rolling cutters which are so inclined on the carrier that their predisposition to lfollow a certain path is utilized to turn the carrier even though it be subject to opposing forces by being on opposite sides of the vertical bit axis. f By inclining the cutters on the presentform of bit, the force they exert to turn the carrier may be added tothe natural tendency of the carrier to turn itself, and so increase the rate of its rotation; or by reversing the cutter inclination, this force may be Jsubtracted from. the natural rotative tendency and decrease the rate of carrier rotation. The latter position gives a sliding 'or slicing motion to the c utters that may be desirable under some-circumstances. Thus lthe carriers may be free to turn as theywiil naturally or they may be influenced by the positioning of the roller cutters.

How the above and other objects and admore'jreadily understood by reference tothe following description and theannexed drawings, in

. Fig. 2 is a vertical median section through the jwhich:

Fig. 1 is a side elevation of a bit constructed in accordance with my invention;

l"it, as on line 2-2 of Fig. 3; i

Fig. 3 is' anhorizontal section .of the bit on.

I I Fig. 4 is an elevation of the bit "as viewed from cutters 20.

` ceive a pluralityof ball bearings 25.

the right of Fig. 1;

Fig. 5 is a section similar to Fig. 3-showing a variational form of bit;

Fig. 6 is a sideelevation of another variationalV form of bit;

Figi? is an horizontal section on line I-"I of Fig. 6 but rotated 90 counterclockwise;

Fig. 8' isa side elevation of a cutter asembly,

withone 'cutter removed and portions broken away to show the construction, provided with avariety of cutter styles and arrangements; and

Fig. 9. is a diagram illustrating the forces acting upon the carriers to cause rotation.' I There is shown in Fig. 1 a bit provided with a shank, generally indicated at I0, having on its upper end threaded pin II-by meansof which Athe shank is'attached to a drill stem for rotation thereby. 'about a,vertical axis. The lower portion of the shank is formed with two depending legs I2 which carry between them the horizontally extending bearing shaft I4. Rotatably mounted upon shaft I4 are two cutter carriers I6 and I1, and about the periphery o f each of these carriers is rotatably mounted va plurality `of rolling Bearing shaft I4 is preferably non-rotatably mounted in shank legs I2 andforms a bearing about which the generally circular, vwheel-like cutter carriers `I6 -and I1 revolve. These carriers thus revolve about a horizontal axis and lie ina generally vertical plane. Shaft I4 is made' with two cylindrical bearing sections I 4a and IIb which, as may be seen in Fig. 3, are of different diameters, each of these sections forming a bearing for one of the jcutter carriers. The two sections are horizontally eccentric on the bearing shaft .so that the yaxes of revolution of the two.

carriers are horizontally spaced, ythe reasons for which will be mentionedlatei.

Shaft I4 is so shaped` that the various diameters oi the several sections increasel progressively from the smallest at one end to the largest at the opposite end of the shaft. This permits the bearing'shaft to be inserted from one side of the bit and pass .through the transverse bores in the cutter' carriers to the position shown in Fig. 3.

after the cutter carriers have been previously assembled and inserted between shank legs I2. The bearingshaft is Vlocked in position by some suitable means, as for example pins 2l at the -ends of' the shaft. Suitably aligned bores are made in the'shank body and .in each end of the shaft to receive a pin 2I which is` threaded to5screw into the shank in order to secure it against removal. These two pins securely lock the shaft against rotation as well as longitudinal displacement.

Bearings are provided to absorb the lateral thrust of the carriers against the shank as well as against each other. Between each carrier and the shank, this thrust bearing comprises an annular groove 22 in the face of shank leg I2 and a corresponding annular groove 23 in the adjoinin'g -face of the rotating carrier. These twoannular grooves are semi-circular in cross section and together form aV ball channel adapted to r- The two bali channels so formed, one at each leg of the shank; are concentricwith thev axis of their respective cutter carriers. Between the two carriers, a similar thrust bearing is formed by an annular groove 2'Iin carrier I8 and a correspond- A ing groove 28 in the other carrier I1. Groove '21 ,passage discharges downwardly through nozzle 39 onto the cutters as they pass beneath the noz- Y largely in `groove 21 and are allowed-la. radial movement in groove 28 for the distance required by the 'relative eccentric movement of vthe two carriers.

-When assembling the bit, groove 21 vis filled jwith ball bearings, while carrier I6 i's at, then carrier I1-is placed -over the rst carrierv to hold theballs in place and next the two 'carriers are inserted between shank legs I2. In order to insert 'balls 25 into the two outside ball channels,

each ofthe ball channels is provided with a straight, preferably horizontal, groove 30 in the shank leg extending between groove 22 and the central opening 'receiving-shaft I4, a'nd a similar groove 3| is provided in the face of .the carrier.

'Ihese two grooves are the same in size' and cross section as grooves" 22 andv 23 and, when in registration as shown on carrier I6 of Fig. 3, together Yform a horizontal passage through which balls 25 may freely mpass to be inserted into 'or removed from the ball channel. When groovey 3i, as a result of'rotation of the carrier, is moved out of registry with the stationary horizontal groove 30, as shown on carrier i1 of Fig. 3, the balls are securely locked within the channel and the carriers themselves are held between the two, portions of the shank. The subsequent insertion of bearing shaft I'4 into positioncloses the open ends of these horizontal passageways so that even when they are in registration, balls 42li4 arenot able to leavethe channel.

Both the replaceable cutter assemblies are as shownin Fig. 8. A

Each cutter carrier I6 and I1- comprises a generally circular, wheel-like body formed with a central transverse b ore Ila to receive shaft I4, an annular groove in each of the two side faces to form theball channels described, and va. plu- -rality of slots 34 'extending inwardlyfrom the carrier periphery and the full width of the carrier body. I n each of these slotsv 3 4, which are hereinafter referred to as radial slots for ease of identification, is placed a cutter 2li mounted to revolveabout an axle pin4 35, and projecting radially beyond the carrier with little or no part of it projecting beyond the parallel sidefaces of the carrier. As maybe seen cest from Fig. 8, pins 35 are inserted in circumferential notches 36 at either side of the radial slots andare wemed into place, as at 31, to complete vthe cutter assembly. While 4cutters 2l! may beof any suitable shape vand diameter, they areI preferablyA substantially cylindrical rollers with axially extendthe cuttersv may be made narrower-'than the others as at 20h.

AExcept in modifications later described, the individual cutters preferably, though not necessar, ily, revolve about Aaxes perpendicular to the axis of the carrier. This is accomplished b y placing pins 35 tangentially about the carrier periphery so'that the cutter axes will lie in the plane of revolution of thecarrier but do not intersect the axis of carrier revolution.

,The upper end of shank Ill-is-formed with an internal fiui'd'passage 38`which receiv sfeircula'- tiony fluid from'the drill stem.- yFlul from this ,s des of the b zle while o ut of cutting contact with the formation.' The. nozzle is located centrally oi' the bit so that itsdischarge strikes both carriers equally. As shown by Fig. 4, the -stream of duid strikes both sets of cutters mainly at one side of their -axes sc that the cutters are spun about pins 35 Y and the fluid reaches all sides of each cutter to insure that ,the cutters are thoroughly cleaned aftereach period of contact with the formation.

' 4 Circulation around the cutters is increased by `passages 42 which connect the bases of successive slots 34 and so form, in effect, a continuous passage around the carrier connecting all the slots lso as to carry'away circulation fluid from around the cutters as the stream from nozzle 39 cleans them. A number of passages 43 lead from the slots to the central opening Ila in the carrier' to .carry fluid for lubrication to bearing shaft I4.

As the bit rotates inthe well beingdx-illed, the

carriers I 6 Vand I1 tend to rotate in oppositedlrections as a result of their contact, through the cutters, with the well walls. -I'itiis'natural tendency for the carriers to rotate will be understood by those skilled in theA art, but Will'be described briefly in conjunction with' Fig. 9 which shows the" carriers diagrammatically in a hole being drilled. The condition may be easily visualized if thecarriers i 6 and I1 and ,shaft 'I4 are compared with two loose wheels mounted 'on an axle. If, while these loose wheels are on a horizontalplane surface, the axle istwisted to turn about a vertical axis intermediate the wheels, the wheels will rotate about .the axle as they roll over the surface, and will turn in such a'mannerthat their forward sides move downwardly.

Thus when the bit is rotated clockwise, as inc ounterclockwise direction as viewed Afrom the outside ofthe bit, that is, thecarriers are moving' downwardly on the sides at which the cutters Contact the formation. 'Ihe forces inducing rotation areV probably greatest at or nearA the botvtom of the carrier -where the rotational forces tend to move the lower side of each carrier in the direction indicated by` arrows 5I, which it vclicated byarrow 50, each carrier rotates in a will be noted are opposite to' each other' and 4 opposite to the direction of rotation of the. bit

as a whole. Yet allforces on the carrier where cutters contact the formation help the rotation since vany such force 53,.although it acts per' i pendicular to the radius 'at the point of application, can'be resolved into two-components, one component 54 parallelto and helping the carrier rotation, andone component 55 perpendiclb; lar to the carrier rotation. 'It willbe noted that 'any component 54 acts 'in the same direction on a carrier asthe force 5I, and that these components actV regardless of whether the carrier ontact's the walls of the hole on one' or both Except for the inclination of the cutters, mentioned below, the "rotational speed of the carriers depends largeiy on their mean distance from the vertical axis of the bit. The two carriers lie on opposite sides l of a vertical plane passing through the vertical axis .of the bit. The-'forces I and 54 on one side of f the plane all act in the same-direction, and 'are opposite to those on the other side of -the plane,

as shownby the opposite rotation of'v the two carriers. Each carrier is placed entirely, or substantially entirely, en one'rside of the vertical bit axis so that forces ofV oppgfsing tendency will not act on the same carrier; and the carriers are placed on opposite Sides of the axis.

Since each carrier rotates naturally as a result of its disposition to one side -of the vertical Vbit axis, 'the direction of carrier rotation is althe two carriers contact onopposite sides of the bit'so that each'takes the lateral thrust of the other. sideof the carrier where the motion is down- Ward, but by reversing the. direction of eccentricity of shaft I4, the cutters will operate on the trailing side of the carriers where the motion* is upward. c

Rotation of the carriers brings every cutter into intermittent cutting contact with the formation and-the path of each cutter as it rolls over the formation is the spiral' resulting from the cornbined rotation of the bit as a whole and rotation of the carrier on the bit. In the construction4 shown in Figs. 1- 4, each cutter -ilrst contacts the formation at a point about horizontally op- .posite shaft I4 and moves spirallydownwardly to a 'point beneath the bit Where' it. leaves the formation as it moves upwardly. This intermittent movement of the cutters o ver the formation is repeated as each cutter is brought successively into and out of cutting contact by rotation of the cutter carrier. Of course, if the cutters first contact the formation on the trailing side of the carriers, then. the cutter path will be an upwardly directed spiral.

The exact path followed by any given cutter will vary according to the speeds of rotation of the shank and cutter carrier, and may vary more orless continuously. The cutters do not roll on any fixed path concentric with the center of the hole nor do .they tend tomove along a preceding, path so that there is little or no- I tracking of the cutters;v and in any event such atendency may be eliminated by changing the style, size, or spacing'of the individual cutters asmentioned above. 'I'he failure o'r loss of one or two cutters will not stop the bit from drilling since it is only a question of time until other cutters will go over those portions of the hole which would have been cut by the missing cutters had they been present, for all cutters at one time or another reach all portions of the hole.

A variational form of bit embodying these same principles of constructionand loperation is shown in4 Fig. 5. In general, the constructionof the bit is identical with that described in connection with Figs. 1 to 4; however, the bit of Fig. 5 is ,designed to provide contact of the cutters on both carriers on both lsides yof the bit, so that the cutters contact the formation over the entire lower half of the carriers. For this purpose the construction has been changed to provide bearing shaft 60 with a single bearing portion so that the two carriers 6l' rotate about coincident axes. Since there is no relatively eccentric movement between the two carriers, the thrust bearing construction may be simplified by eliminating the wide, shallow groove'A 28 and supply-u ing both carriers with a ballgroove 21 on their mutually adjacent faces.

'Ihe path'of any carrier over the formation will be a spiral as before described, but will also include a second spiral beginning Aat the bottom The cutters operate on the advancing of the hole and extending upwardly to a point about level with 'the shaft 6| l where the cutter contact ofthe bit shown in the preceding` gures.

Figs. 6 and '7 illustrate another variational form of drill bit which also has the same general construction as the forms heretofore described. Bearingshaft is offset from the vertical bit axis and has two bearing sections a and 65h which, although of different diameter, are 'concentric so that the two carriers 6l rotate about coincident axes, as do carriers tl in Fig. 5.

l However, the over-al1 vdiameter of carriers 61 is less than that of carriers 6| with the result that the cutters on each carrier contact the formas tion on only one side of the bit, but bothcarriers contact the formation on the same side of the bit. Shank body I0 has an extension l0a which connects legs i2 on the back, or 'non-cutting side o'f the bit. Each of the legsl Il. is proinstead of being parallel to or lying in said plane..

'I'he pins 35 are here shown inclined in what may be called a forward direction since'they are in'- clined in that direction which'brings them more nearly perpendicular to the spiral path of the cutter over the formation, or at least a portion of that path. By so inclining these pins, the direction in which the cutters will move with a true rolling motion coincides more nearly with the actual spiral path which they follow as a result of the combined bit and carrier rotation, so that.

the tendency of the cutters to move in this direction of true rolling motion is taken advantage of to assist or increase the rotation ofA the carrier about shaft 65.

From this consideration it will be seen that when pins 35 lie in or parallel to the plane of carrier revolution, as in Fig. 5, the axle pins and the cutters thereon are in what'may be termed a neutral position, since there is no tendency `to assist the rotation of the carrier and yet there is little opposition to it. On the other hand, if the pins are inclined to the plane of carrier revolution oppositely to that shown, they are then in what may be calleda backwardly inclined position, since the direction of true rolling motion has been moved farther away from the actual path which the cutters will follow. This results in retarding or slowing up the rate of carrier revolution and causes the cutters to have a greater slicing action, since theyv must necessarily` slide somewhat as they move over the fo'rmation. 'This .latter may be desirable in certain types of formations.

In order to `prevent assembling the bit with the cutters inclined in the direction other than that intended, shaft 65 has been made with bearing portions of two different diameters, and the ball channels are made of 'different diameters about the shaftso that the bit can be assembled in only that position which is intended.

From this construction it will be seen in all forms of the bit that not only has each roller vided with a rib i2b which bears against the annotato portion of the total cutters which is activeer engaged with the formation will vary with the number ofV cutters and their' placement on the.

carriers as well as the disposition of the carriers themselves,'but in general the proportion of cutters inactive engagement with the formation at any time will not exceed one-half of the total number..

Having described various embodiments of my invention, it will 'be at once apparent that changes may be made in the arrangement and construction of the variousparts, and that vari- -ous other embodiments may be constructed without departing` from the spirit and scope of my invention, and therefore the annexed claims are to be construed as illustrative of rather, than restrictive upon \\the broader aspects of my invention.

I claim as my invention:

-1. A cutter assembly for a deep well rotary earth boring tool comprising a generally circular,

' wheel-like cutter carrier adapted to be rotatably mountedon a tool body and having a plurality of radial slots around the carrier; a plurality of central axis, a plurality of radial slots in the car- '.zircinnierentialiy` extending pins welded to` the carrier; and a roller type cutter in each slot rotatably mounted upon one of said pins.

2. In a deep well rotary earth boring tool, a rotatable cutter carrier comprising a generally circular, wheel-like bodyadapted to turn about a labout the periphery of the carrierythe carrier having a central transverse opening to receive a bearing member about which the carrier rotates,

and an annular groove. iny one of the two side races to form a portion of a bali channel adapted to receive balls to provide lateral. bearing for the cutter carrier. l

d. .A cutter assembly for a deep well rotary earth boring tool comprising a generally circular, 'wheel-like cutter carrier, and a plurality .of lcut'- ters rotatablyrmounted about the periphery of the carrier; the carrier having a central transverse .opening to receive a bearing member about which the carrier rotates, and an annular groove tivelyv shallower and wider to permit radial move.

ment of balls riding in the groove.

5. A cutter assembly for a deep well rotary earth boring tool comprising a generally circular,

.wheel-like cutter carrier; a central transverseopening inthe carrier to 'receive a bearing sha`ft about which the carrier rotates; a plurality of radial slots around the periphery of the carrier; la cutter-rotatably mounted in each of the slots;

`spective passageways.

a continuous passage connecting the bases ofA slots to conduct circulation iluid away from the cutters; and a plurality of passages leading from the slots to the central opening to conduct a circulation iluid to the bearing shaft from the slots.

6.A' cutter assemblyfor a deep well rotary earth boring tool comprising a generally circular, AWheel-like cutter carrier; a plurality oi' radial slots around the periphery of the carrier; and a cutter rotatably mounted ineach oi the slots, alternate cutters being similar and successive cutters diiering in the shapefand spacing .of teeth.

'7. A cutter assembly for an earth boring tool comprising a wheel-like carrier adapted to be rotatably mounted on the tool body, the carrier hating a plurality of slots extending from the carrier periphery radially inward-and notches adjoining each of the slots; axle pins welded in pairs of notches and extending acrosseach slot;- and a toothed, substantially cylindrical roller cutter rotatably mounted on each pin to turn within the slot..

8. A cutter assembly ior an earth boring tool ,i comprising' a carrier adapted toi be rotatably mounted on the tool body,a plurality of'generallyA radial slots in the' carrier, and a cutter positioned in each of said slots and rotatably? supported by Psaid carrier.

9. A cutter assembly as in claim 8, wherein said slots extend to the periphery of said carrier.

l0. A cutter assembly as in claim 8, wherein lsaid slots are circumferentially spaced around said carrier.

11. A outter'assembiy foren earth boring tool comprisin`g a carrier adapted to be rotatably mounted on the tool body, means providing one or more generally radial slots on the carrier, and* at leastone cutter in each .slot rotatably supported by said carrier. f

"12. A cutter assembly for an earth boring tool comprising a .carrier adapted to be rotatably mounted on the tool body, the carrier having a` plurality of slots spaced around its periphery, shafts extending across each slot and supportedv by said carrier, and at least one cutter carried,

by. each shaft for rotation relatively to the carrier.

13. `A cutter assembly as in claim 12, wherein cach shaft is xedly secured to the carrier, each cutter being rotatably mounted on its shaft.

14. A carrier for arotary earth-boring tool cutter assembly, comprising a wheeL-like body, a Ytransverse central opening in said body adapted to receive a bearing, and a plurality of spaced circumferentially arranged slots on said carrier each adapted to receive a roller cutter.

15. A carrier asin' claim 14, wherein said slots extend generally radially inwardly from the periphery of the'can'ier. f

1S. A vcarrier as in claim 14, wherein said central opening and slots are connected by rey1'?. .A carrier for a cutter assembly, comprising a wheel-like body, a plurality of generally radial slots extending around the body, and a 18. `A cutter assembly for an earth boring tool comprising a carrier adapted to be rotatably mounted onthe tool body, spaced supporting means on thev carrier; and a cutter rotatably carried by and between said supporting means.

19. A cutter assembly for an earth boring tool comprising a carrier adapted to be rotatably mounteaon the tooi body, spaced supporting plurality of circumferential notches in the body extending from each radial slot.

means on the carrier, and a. plurality cf cutters rotatably carried by and between said support-4 ing means, said cutters being spaced around thel carrier adapted to receive `a. bearing, and one or more rotatable cutters carried by said carricr, the axes of said cutters lying in a plane including the central opening and being perrs pendicular to the .axis of said opening.

JOHN A. ZUBLIN. 

